Ore-concentration process



UNITED STATES PATENT OFFICE.

WALTER A. SCOTT, OF RIVER FOREST, ILLINOIS.

ORE-CONCENTRATION PROCESS.

No Drawing.

reagents and procedure. In view of the widespread knowledge of the flotation process as now practised but brief reference will be made herein to the art-as it now exists. In this process the ore is quite finely ground, the. degree of fineness depending on the minuteness of subdivision of the ingredient which is to be'saved and other factors, the grinding generally being performed in water. The ore thus reduced to a freely-flowing pulp is subjected to the action of gaseous bubbles and some substance or substances which have the effect of causing the valuable particles to adhere to the bubbles and form a froth, the froth with its content of valuable mineral being removed and forming the concentrate. Various methods have been employed heretofore for introducing the various reagents. The substances used for causing the valuable particles, generally metallic sulfids, to adhere to theibubbles and for causing the formation of a froth'of sufficient persistence to permit its removal by skimming, overflow or -other-.

wise, being for the most part oils or oily substances, have customarily been, referred to generically as oils, although many substances suitable for the purpose, such as various coal tar products, alcohols, etc., are not oils. In this application I shall refer to all of these "substances as oils for want of a better generic term. The frothing function of the oils employed is more or less d1stinct from the function of setting up the selective afiinity of the bubbles for the deslred particles, generally metallic sulfids, as d1stinguished from'the particles which are to be rejected in the case of ores the gangue particles. some oils are very-eflicient in the ,matter of creating a selective affinity between the bubbles and the desired particles to the exclusion of the undesired partlcles but at the same time are quite ineflfective' Specification of Letters Patent.

Application filed July 8, 1919. Serial No. 309,461.

Patented Jan. 11, 1921.

in the matter of imparting suflicient persistency to the bubbles to cause the formation of a froth of suflicient permanence to permit of its separation from the remainder of the mixture on which it floats. Other o ls cause the formation of a froth of sufiic1ent persistence but do not confer on the bubbles any or a sufficient discriminative attraction for the desired particles as distingu'ished from the waste particles which are to be rejected. It will be understood,

'as above stated, that throughout this ap- 'pl 1cat1on 'I use the term oils to include a w1de varlety of substances many of which are not in fact oils but have analogous properties in operations such as here discussed.

In the treatment of some ores various acids and alkaline substances and various salts and other chemical compounds increase the efliciency of the process. Herein I shall refer to all the substances useduin the process as reagents, whether oils, acids, alkaline substances, salts or other chemical pompounds. Oils whose principal function is or -which are used more particularly for the function of increasing the persistency of the froth I term frothers, and oils. whose principal function is or which are more particularly used for the function of creating or increasing the selective aflinity of the bubbles for some particular ingredient or ingredients of the mixture I shall termcollectors. a

. In the flotation process as heretofore practised the bubble-forming gas, generally air, has been introduced into the ore pulp either by mechanical agitation which has the effect of beating the air into the pulp or the air has been introduced in finely divided form through a porous bottom provided in the vessel containing the pulp. The oil has heretofore generally been added directly to the pulp and mixed therewith by agitation, but in some instances the oil, either the vapor of a substance liquid or solid under ordinary conditions or a substance that is gase- 4 ous under ordinary conditions, has been' mixed with the air which is introduced into rounding liquid and the solid particles in v required conditions.

one described by F. J.

As the phenomena of flotation depend largely, if not wholly on the properties of the interface between the gaseous interior of the bubbles and the surrounding liquid I propose to form the substances necessary for creating the required properties at the precise place where these properties are utilized, namely at the interface, thereby effecting an economy of the reagents employed, utilizing the properties inherent in the various reagents at the moment of formation, 2'. 6. when in the nascent state, and alsoany thermal and electrical conditions that are incident to the chemical reactions occurring at the interface between the bubble and liquid. I

effect this object by introducing in gaseous or minutely subdivided liquid or solid form with the air forming the bubble some substance that will react chemically with some ingredient suspended or dissolved in the pulp. For instance, it has heretofore been proposed to dissolve a soap in the pulp and to decompose the soap by means of a mineral acid also mixed with the pulp, thus freeing the fatty acid contained in the soap by reasonof its displacement by the mineral acid which combines with the alkali of the soap. In the application of my invention I dissolve the soap in the pulp as formerly, but instead of also adding the mineral acid to the pulp I introduce the mineral acid in gaseous form in admixture with the air. The result of this procedure is that the gaseous mineral acid within the bubble reacts with the soap in solution in the pulp. This reaction takes place at the interface between the gaseous contents of the bubble and the surrounding liquid with the result that the fatty acid oelic acid for instance, is freed at the precise place where its properties are to be utilized, namely in the interfacial film. Among the mineral acids that can be used in this way are hydrochloric and nitric acids, and in fact any suitable acids that can be maintained in the gaseous condition while being introduced with the bubbleforming air or other gas. The mineral acids may also under some conditions be introduced in a finely divided liquid or solid form as a spray or fog in admixture with the bubble-forming gas.

In the application of rocesses such as the yster in his United States Patent No. 1,203,373 in which he utilizes the properties of calcium chlorid, cal-. cium nitrate and sodium carbonate my invention can be used with advantage' The pulp may contain calcium carbonate in solution and hydrochloric acid in gaseous form may be introduced in admixture with the air, under which conditions the hydrochloric acid contained in the bubble will react at the interface with the calcium carbonate in the pulp giving rise to calcium chlorid in the interfacial film. Nitric acid introduced in admixture with" the bubble-forming air will likewise react with cal ium carbonate contained in the pulp giving rise to calcium nitrate in the interfacial'film, and carbonic acid gas introduced with the bubble-forming air will react with sodium hydroxid in the pulp to form sodium carbonate in the interface. In his United States Patent No. 1,203,374 Lyster refers to the use of sodium chlorid, which according to my invention may be formed at the interface surrounding the bubbles by dissolving sodium carbonate or other sodium salt in the pulp and introducing hydrochloric acid gas in admixture with the bubble-forming air. Similar illustrations of the use of my invention might be multiplied indefinitely.

In many instances the effectiveness of the flotation process is greatly increased by making the pulp acid in reaction by the addition of sulfuric or other mineral acid, but some ores contain so large an amount of calcium 95 carbonate or other acid consuming ingredient as to render it impossible to impart an acid reaction to the pulp without the use of a prohibitively large amount of acid. In such cases the effectiveness of the acid may be obtained by introducing it in gaseous form in admixture with the bubble-forming air, hydrochloric andnitric acids being suitable for use in this manner. By this means the acid is brought to the bubble-water interface without coming into contact with and being uselessly consumed by the carbonate contained in the ore and the modifying effect of the acid is obtained with a minimum consumption thereof. My invention, in its 110 broader aspect, therefore includes the introduction of certain reagents in gaseous or finely divided liquid or solid form in admix ture with' the bubble-forming air in order to prevent useless and wasteful consumption of such rea ents by substances contained in the pulp, w ether such substances occur naturally in the ore or are introduced into the pulp as a part of the process or as a part of some other operation to which the ore is subjected during treatment. 1

:While in the claims I use the term ore it will be understood that my invention is applicable not only to the original ore but also to any .intermediate'product derived from theore as well as in some instances to substances other than ores and their derivative roducts. By the term "bubble-forming gas refer to the gas which is utilized principally for buoyancy, this being practically always air. I. use the term modifying substance to designate reagents other than those oils which function principally as frothers and collectors, for instance various salts, acids, etc., which modify the action obtained by the use of oils, which salts, acids, etc., have generally in themselves no frothing and collecting power, or at least do not have such power to any useful degree when used alone. I also in theclainis use the term flotation agent as a generic expression to include both oils and modifying substances as above defined. WVhile the theory of the flotation process has not been reduced as yet to anything approaching certainty I have herein made use of certain quite widely accepted theoretical explanations in order to make the description definite, but it will be understood that my.invention resides in the operations described, which operations have the practical advantages referred to regardless of the adequacy of-present theories of flotation. As hereinbefore indicated my invention includes the introduction of certain reagents in admixture with the bubble-forminggas, which step may be utilized in some instances in;

1. In the flotation precess of concentrating ores, the operation of reducing the ore to 'a freely-flowing pulp, forming in said pulp bubbles containing a substance capable of reacting chemically with a substance contained in the pulp thereby formin a fiota-- tion agent, and separating the hub les with the solids adhering thereto from the remainder of the pulp.

2. In the flotation process of concentrating ores, the operation of reducing the ore .to a freely-flowing pulp, introducing into said pulp a bubble-forming gas in admixture with a substance capable of reacting chemically with a substance contained in the pulp, thereby forming a flotation agent.

3. In the flotation process of concentrat ing ores, the operation of reducing the ore to a freely-flowing pulp, introducing into said pulp a bubble-forming gas'in admixture with a substance in gaseous form which is capable of reacting chemically with a substance contained in the pulp, thereby forming a flotation agent. 7

4. In the flotation process of concentrating ores, the operation of reducing the ore to a freely-flowlng pulp, introducing a bubble-forming gas into said pulp, forming a flotation agent in the interfaces between the bubbles and pulp by introducing in admixture with the bubble-forming gas a substance capable of reacting chemically with a substance contained in the pulp.

5. In the flotation process of concentrating ores, the operation of reducing the ore to a freely-flowing pulp, introducing a bub ble-forming gas into said pulp, forming a flotation agent in. the interfaces between the bubbles and pulp by introducing in admixture with the bubble-forming gas a substance in seous form which is capable of reacting c emically with a substance contained in the pulp.

In testimony whereof I-have subscribed my name. I

" WALTER A. SCOTT. 

